Abstract

Many physiological and pathological conditions are associated with a change in the crystalline lens transmittance. Estimates of lens opacification, however, generally rely on subjective rather than objective measures in clinical practice. The goal of our study was to develop an improved psychophysical heterochromatic flicker photometry technique combined with existing mathematical models to evaluate the spectral transmittance of the human ocular media noninvasively. Our results show that it is possible to accurately estimate ocular media density in vivo in humans. Potential applications of our approach include basic research and clinical settings on visual and nonimage-forming visual systems.

M. Ozolinsh and P. Paulins, “LED based dual wavelength heterochromatic flicker method for separate evaluation of lutein and zeaxanthin in retina,” presented at the International Symposium on Biomedical Engineering and Medical Physics, 10–12 October 2012, Riga, Latvia.

M. Potash and B. Jones, “Aging and decision criteria for the detection of tones in noise,” J. Gerontol. 14, 953–960(1997).

Owsley, C.

Ozolinsh, M.

M. Ozolinsh and P. Paulins, “LED based dual wavelength heterochromatic flicker method for separate evaluation of lutein and zeaxanthin in retina,” presented at the International Symposium on Biomedical Engineering and Medical Physics, 10–12 October 2012, Riga, Latvia.

Paulins, P.

M. Ozolinsh and P. Paulins, “LED based dual wavelength heterochromatic flicker method for separate evaluation of lutein and zeaxanthin in retina,” presented at the International Symposium on Biomedical Engineering and Medical Physics, 10–12 October 2012, Riga, Latvia.

Visual Res. (1)

Other (3)

M. Ozolinsh and P. Paulins, “LED based dual wavelength heterochromatic flicker method for separate evaluation of lutein and zeaxanthin in retina,” presented at the International Symposium on Biomedical Engineering and Medical Physics, 10–12 October 2012, Riga, Latvia.

(A) Photo of the annulus with a long exposure time resulting in the color being a mixture of the 410 and 560 nm. The vertical reflections on the sides come from the chin rest metal frame, and one in the lower part of the annulus from the chin rest. (B) Corresponding luminance map with Photolux system [17]. The observed high homogeneity of the annulus is due to the use of multiple diffusing sheets.

Ocular media density measurement protocol. After 45 min of DA, subjects performed a threshold detection training phase with the nonpreferred eye (‘nondominating’, left for majority of the subjects) and were instructed to increase the light intensity of the 560 nm light until the detection of the annulus was flickering. Training was followed by a threshold detection procedure for 560 and 410 nm lights with the preferred eye. In a second step subject had to detect their CFF by increasing (ascending) or decreasing (descending) annulus flickering frequency. In the last step of the protocol (flicker fusion) the subject had to abolish or minimize their perception of flickering by adjusting intensity of a 410 nm light either by increasing it (UP) or decreasing it (DOWN). Flicker fusion was made using both eyes, starting with the nonpreferred eye.

Sensitivity of the method for rhodopsin parameters. Separate analysis for rhodopsin peak sensitivity λmax (left, above) and rhodopsin axial pigment density drh (right, above). Values used by us are λmax=495nm and drh=0.40. The nomogram of Govardovskii et al. [13] includes the β-band; thus the short-wavelength lobe is elevated. The lights are normalized to have the same total photon density; thus the green 560 nm has a lower peak value.

Relative spectral transmittance of the three age groups as derived using the virtual age with the model of [9]: young group (top, red curve), middle-aged group (middle, blue curve), and elderly group (bottom, green curve). Young, agevirtual=23.38(−7.6+5.0); middle, agevirtual=40.32(−3.8+3.6); elderly, agevirtual=88.81(−1.8+2.1).